Oil-pressure-controlling device for big inertial load

ABSTRACT

Cavitation and stalling of a hydraulic motor coupled to a large inertial load is prevented by a self-operating valve sensitive to applied oil pressure and the pressure of oil returned to the sump for controlling the pressurized fluid operating on the hydraulic motor.

I United States Patent [151 3,640,069 Sugahara et al. Feb. 8, 1972 [54] OIL-PRESSURE-CONTROLLING [58] Field of Search ..91/437,447; 137/596.12; DEVICE FOR BIG INERTIAL LOAD 60/105 [72] Inventors: Takashi Sugahara; Minoru Suzuki; [56] References Cited Tadayuki lfilkunaga, all of Akashi-shi, Hyogo; Shozo Fukushima, Kobe, all of UNITED STATES PATENTS Japan 2,651,324 9/1953 Hodgson et a1. ..137/596.12 [73] Assignee: Kawasaki Jukogyo Kabushiki Kaisha, 3,313,316 4/1967 Thomas ..91/437 Kobe-shi, Hyogo, Japan Primary ExaminerWi11iam L. Freeh [22] Flled 1969 Assistant ExaminerRichard E. Gluck [21] A NO 850,034 Att0rney-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT [30] Foreign Application Priority Data Cavitation and stalling of a hydraulic motor coupled to a large Aug. 14, 1968 Japan ..43/58 152 i i load is prevented by a se|f operating valve sensitive to applied oil pressure and the pressure of oil returned to the [52] U.S.Cl ..60/105,417/237,417/87, Sump f controlling the pressurized d operating on the 417/291, 91/437, 91/447, 91/461 hydraulic motor [51] Int. Cl ..F15b ll/08,F15b 13/04, F01k 13/00,

F22b 33/00 5 Claims, 7 Drawing Figures 46 I I 38 37 as 44'39 '49' 4 35 37 PATENIED FEB 8 15172 SHEET 1 [IF 3 PATENTED FEB 81972 3,640,069

sum 3 UF 3 Fl G 6 68 67 73 68' OIL-PRESSURE-CONTROLLING DEVICE FOR BIG INERTIAL LOAD BACKGROUND OF THE INVENTION 1. Field of the Invention the present invention relates to oil-pressure-controlling devices particularly useful for controlling large inertial loads.

Heretofore, in stopping a: hydraulic motor or a hydraulic cylinder coupled to a large inertial load, the inlet and outlet of the motor or cylinder is closed by a switch over valve and a relief valve is opened for creating a bypass to kill the energy of the inertial body. In such prior art, when the inertial body is large, the pressure oil quantity is increased and the circuit pressure at the moment of stoppage is rapidly increased to excess. Where the return circuit has no resistance during the movement of the hydraulic motor or cylinder, the inertial load is abruptly moved in one direction and so-called stall is brought about, whereby a cavitation is formed in the motor or cylinder and sometimes a loud noise is created.

SUMMARY OF THE INVENTION DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of the device in accordance with an embodiment of the present invention.

FIG. 2 is a sectional view of the device shown in FIG. 1 taken along the lines A-A and C-C.

FIG. 3 is a sectional view of the device shown in FIGS. 1 and v 2 taken along the line B-B.

FIG. 4 is a sectional view of the device shown in FIG. 2 of the different operating situations, and

FIGS. 5A, 5B and 6 are sectional views and an enlarged view thereof of an essential part of the device in accordance with another embodiment thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings showing an embodiment of the present invention, as best shown in FIG. 1, a spool valve 2 and a relief valve 3 are arranged in parallel with each other in a common housing 1, and these two valves 2 and 3 have an internal structure as shown in FIGS. 2 and 3, wherein the sectional views of the spool valve 2 and relief valve 3 are inverted with each other, that is, one of which is positioned upside down. The reference characters P, T, V, MF and W in FIG. 2 denote respectively a pump, tank, directional control valve, hydraulic motor and an inertial load for the device in accordance with the present invention.

On the periphery of the housing 1 outside of the spool 4 and within the spool valve 2, four recessed grooves 16, 14', 15, and 17 are provided from left to right. The grooves 14' and 15 are connected with each other through passages 14 and 15 and inlets and outlets A B,., on the left side thereof, the pressured oil is directed through the passage 14, recessed groove 14', radial holes 60 of the spool 4 and into the axial bore 18 at the center of the spool 4, and pushes the poppet valve 7 to the left against a weak spring 8. It then reaches the groove 16 through a hole 61 of the spool 4. The recessed groove 16 is connected to an annular chamber 31 extending outside of the nozzle 41 disposed at two inlets and outlets of the relief valve 3 shown at the upper portion in FIG. 2 through a passage 63 shown in FIG. 3. The pressure oil reaching groove 16, therefore, flows further up to the hydraulic motor MF.

Since the pressured oil directed up to the passage 14 of the spool valve 2 from said inlet and outlet A is further directed to the chamber 52 on the left end of the spool 4 containing a spring 6 through another passage 29, and the pressure oil is also directed to a damping chamber 27 constructed by a projected portion of a plug 9 and a cover 13 through a check valve, the spool 4 is moved to the right compressing the spring 6 on the right through washer 62', whereby the spool valve 2 is brought into the position shown in FIG. 4. In this position, for the first time, a return circuit is formed, the hydraulic motor MP is started and the load W is driven. The return circuit comprises the hydraulic motor MF, an annular chamber 32 on the periphery of the nozzle 42 in the relief valve 3, a passage 63, recessed groove 17, cut portion 21 of spool 4, a recessed groove 15', a passage 15, an inlet and outlet B,., a directional valve V and a tank T.

As a result of the above-described operation, the pressured oil needed for accelerating the hydraulic motor MF is supplied to the hydraulic motor MF. If an excessive amount of pressured oil is supplied to the hydraulic motor MF and the oil pressure in the supplying circuit is increased over a preset pressure because of a large inertial load, the excessive oil pressure is further extended in the relief valve 3 in FIG. 2 to a spacing 54 through an annular chamber 31, a nozzle 41, a housing groove 44, four holes 64, and a recessed groove 49 of the left side valve cylinder 35, whereby the oil in the spacing 54 acts on the valve seat cylinder 39 disposed in the housing at the central portion of the relief valve 3 to push the valve seat cylinder 39 to the right. When the valve seat cylinder 39 is pushed to the right, a space is formed between the left end of the valve seat cylinder 39 and the plunger 33, whereby the pressured oil is further guided into the bypass passage 45 at the center of the valve seat cylinder 39 to push the plunger 33 to the left against the force of the spring 43 and broaden the flow-in port of the bypass passage 45. A portion of the excessively pressured oil further flows into a chamber 48 in the cap 38 through a choke hole 40 at the head of the plunger 33, an oil chamber 46 in the plunger 33, a central hole of a rod 36, and a central passage of a spring seat 37, these elements acting together to form a high-pressure crossover relief valve means, whereby the spring seat 37 is moved to the right by oil pressure until the spring seat 37 is brought into contact with the step portion of the valve cylinder 35. Thus, the spring 43 is compressed from opposite sides; by the plunger 33 from the right and by the spring seat 37 from the left.

The pressured oil flowing into the bypass passage 45 pushes another plunger 34 located in a valve cylinder 35' disposed to the right of said valve seat cylinder 39. When the plunger 34 is Y pushed to the right, for a moment the pressured oil is released from the space between the right end of said valve seat cylinder 39 and the plunger 34 by the pressure corresponding to the compression force of the spring 43' in the case when the spring seat 37 is at the right end. But just as the case described before, the spring 43' on the right is compressed by the plunger 34 moving to the right and by the spring seat 37' moving leftward, and the relief valve 3 is brought into the position shown in FIG. 4. Thus the spring 43' of the relief valve on the right is set for opening the opposite ends of the bypass. The pressured oil is released to the return circuit through a groove 49 of the valve cylinder 35', a hole 64', a housing groove 44, a nozzle 42, annular chamber 32 and return conduit 63.

If the pressure is reduced lower than the present pressure valve, the plungers 33,34 move to the center by the springs 43,43, and then the spring seats 37,37 retire to the left and right with delayed timing caused by the choke holes 40,40. Thus, the plungers and the spring seats are returned to their initial positions. The circulation of the pressured oil to the hydraulic motor MF and from the hydraulic motor MP is made through the annular chambers 31,32 on the periphery of the nozzle, passages 63,63, the spool valve 2 and the directional control valve V. When the directional control valve V is moved back from the left position to the neutral position, the inlet and outlet parts A and B,, in the spool valve 2 in FIG. 4 are both connected to the tank T, wherebythe internal pressure in the spring chamber 52, which has been guided through the inlet and outlet part A,,, the passage 29 and the spring chamber 52, is reduced to the same pressure which is equal to the pressure in the spring chamber 53 on the right. The spool 4 returns to its initial neutral position by the spring 6' of the right chamber 53. The connection of the housing groove 17 with the groove through the cut portion 21 of the spool 4 is cut 011', thereby closing the return passage of the hydraulic motor MF. As for the relief valve 3, even if the valve seat cylinder 39, both plungers 33,34 and the spring seats 37 ,37 are moved in switching of directional control valve V, the relief valve 3 is moved back to its initial position.

In case that the hydraulic motor MP is rotated in the same direction by the inertial load when the valves are moved back to their initial position, in the return passage from the hydraulic motor MP to the housing groove 17 of the spool valve 2 through the annular chamber 32 of the relief valve 3, high pressure is achieved since the passage between the groove 17 and the groove 15 is cut off. Ifthe pressure reaches above the present pressure of relief valve 3, pressured oil moves into the bypass 45 of the relief valve 3 from nozzle 42 and the relief valve on the left of the relief valve 3 in FIG. 4 operates. By the operation of the left-hand relief valve, the oil of the quantity corresponding to the number of revolutions of the hydraulic motor driven by the inertial load jets from nozzle 41 on the left and is supplied to the hydraulic motor MF which is pumping, whereby the breaking torque for the inertia of the load W is maintained constant despite any revolution and stall is prevented from slowing down and stopping the oil pressure motor MF. Thus, the jet flow out of the nozzle 41 is at a negative pressure at the outlet of the nozzle and the oil in the annular chamber 31 in the vicinity of the jet flow is sucked out. In the case that the oil in the annular chamber 31 is sucked out too much and there is a shortage of oil, the oil in the tank connected to the inlet and outlet A, through theleft poppet valve 7 of the spool is addedthereto/I'he jet flow is reduced in speed as it approaches the inlet of the motor and the pressure thereof is recovered. By this ejector effect, the cavitation of the hydraulic motor MP is effectively prevented.

The controlling device in accordance with the present invention, when the directional control valve V is switched abruptly or extremelyslowly, prevents the stall of the oil pressure motor which might be brought about by the inertia of the big load, thereby making the hydraulic motor operate stably.

In the case that the directional control valve V is abruptly returned to the middle position during the neutral and the left or right position or in the case that the hydraulic motor is brought into a stall condition, the pressure in the suction passage for the hydraulic motor is instantaneously lowered and the pressure in the spring chamber 52 connected to the suction passage through the passage 14 in the spool valve 2 and the passage 29 is also lowered, whereby the spool 4 is returned to its neutral or near to neutral position. Therefore, the connection of the groove 17 with the groove 15 through the cut portion 21 is severed or extremely limited and the oil pressure in the return oil passage is abruptly increased. Since, at this moment, the pressure in the spring chamber 52 recovers due to the existence of the supply pressure oil in the passage 14. from the directional control valve V, the spool 4 is exerted by a force to push it to the right. But, since the pressure oil in the damping chamber 27' constructed with the right end projected portion of the spool 4 and the cover 13 is connected with the right spring chamber 53 only through a slight space 28 and the passage 25 is closed by a ball of the check valve, the movement of the spool 4 to the right is controlled by the choke effect of the pressured oil. The variation of the pressure in the return circuit of the hydraulic motor, therefore, is controlled at minimum and the motor is controlled to operate at a constant speedaccording to the oil quantity supplied and prevented from stalling.

FIG. 6 is a sectional view showing another embodiment of the relief valve 3, and FIGS. 5A and 5B are sectional views of the relief valve shown in FIG.6 for explanation of the principle of the operation thereof.

In FIG. 5A, the reference character 67 denotes a poppet valve provided with a sharp head of an obtuse angle 20 on the head portion of the valve rod thereof having a cross-shaped section as shown in FIG. 5B, 68 denotes a valve seat provided with an inlet and outlet 71 for oil flow from outside and a shaft hole 69 of relatively small diameter at the center thereof, and 72 denotes a valve cylinder. The sharp head of the poppet valve 67 is fitted against the open end of said shaft 69 of the valve seat 68 and inserted into said valve cylinder 72, and both of them are pressed against each other by means of springs 73,74. Oil flow directed into the shaft hole 69 at the center of the valve seat 68 from the inlet 71 is accelerated by the shaft hole 69 of small diameter up to the high speed of V, and intensely hits the sharp head of the poppet valve 67. When the oil flow hits the sharp head, the component of flow thereof in the moving direction of the poppet valve is lowered to V V /E V By the reaction of the lowering of the speed, and by the pressure loss by friction when the oil passes through the crossshaped valve rod of the poppet valve at the speed of V;,, a large driving force is exerted on the popper valve 67, whereby the pressure override characteristic is improved.

In the relief valve shown in FIG. 6, the valve mechanism having good pressure override characteristics shown in FIG. 5 is employed instead of the valve mechanism comprising the right and left plungers 33,44, springs 43,43, and spring seats 37,37 employed in the relief valve 3 shown in FIGS. 1 and 4. The action of the hydraulic system for the hydraulic motor MP in response to the increasing of the pressure is more faithful and sensitive, and the acceleration, slowing down and stopping of the hydraulic motor is more effectively achieved. In FIG. 6, the members equivalent to. the members shown in FIGS. 1, 4 and 5 are identified with the same reference characters as those used in FIGS. 1, 4 and 5,v and the explanation of the action thereof is omitted.

The present invention is characterized by the following five features: There is provided a relief valve 3 which is operatively disposed with the oil return passage and the oil supply passage and has valve devices disposed on theopposite sides of the valve seat cylinder 39 and has a bypass 45 opening when the oil pressure is increased. The abrupt and excessive increasing of the pressure in the oil pressure passage is prevented by two steps of setting the pressure for opening the valve by the bending of the springs 43,43 used for opening the valve device in the relief valve 3 and setting of the pressure for closing the valve by the movement of the spring seats 37,37 with the bent spring. The ejector effect is gained by ejecting the oil flow which is released from the relief valve through a bypass 45 of the relief valve 3, through the nozzles 41,42 disposed at the center of the annular chambers 31,32 forming a part of the flow passage for the hydraulic motor MP. The movement of the spool 4 is stabilized and stall of the load is prevented when the pressured oil supply passage for the hydraulic motor MF is switched by the directional control valve and then the oil pressure of that passage is varied by the inertial load. This is achieved by mounting the spool valve 2 including a spool 4 for opening and closing the pressure oil returning passage from the hydraulic motor by automatically moving right and left with the supplied oil pressure, between the pressure source P and tank T, and said relief valve 3, and by providing damping chambers 27,27 between the projected portions at the opposite ends of said spool 4 and the covers 13,13 of the housing. The override characteristic of the relief valve 3 is improved by the driving force acting on the poppet valve 67 by making the valve device of the bypass passage in the relief valve 3 of such construction that the sharp head portion of the poppet valve 67 faces the open end of the small shaft. hole 69 of the valve seat metal 68.

Accordingly, with the oil pressure controlling device of the present invention, various advantages as follows are gained: In the case that the device is adapted to an oil pressure motor or oil pressure cylinder carrying a large inertial load, there is no need to employ or select a complex valve and the like which are employed in the prior art, and the system is very easily controlled just by putting the device in accordance with the present invention between the oil pressure motor MF or oil pressure cylinder and the switch over valve V. Since a pair of valve devices are disposed at the opposite sides of a common bypass as a relief valve, the two valve devices serve as a check valve or a relief valve according to the direction of the movement of a motor or cylinder and each valve has two steps of set pressure, whereby the abrupt and excessive increasing of pressure when the motor or cylinder is stopped is prevented. Since the oil flow flowing out of a valve port at the end of the bypass of the relief valve 3 through the bypass is ejected out of the nozzle at the center of the annular chamber in the oil pressure passage for the motor or cylinder, the oil around the nozzle is sucked by ejector effect and cavitation is prevented. Besides, by providing a spool valve 2 for the relief valve 3 in the same housing 1, the oil passage is automatically switched over by switching the supplied oil pressure, and at the same time the oil passage is automatically opened or closed by cutting off the pressured oil supply, whereby the inertial load is accelerated, rotated in the opposite direction, slowed down, and stopped. The movement of the spool 4 in the spool valve 2 is controlled by providing a pair of damping chambers 27,27 between projected portions disposed at the opposite ends thereof and the end plate of the housing then making it difficult for the oil therein to leak out. The operation for preventing the stall is made substantially stable even if the pressure varies in the supply oil passage. Moreover, by providing the mechanism of poppet valve 67 and the valve seat metal 68 as shown in FIG. 5 in the valve device of said relief valve 3, the operation and effect of the relief is further improved.

We claim:

1. An oil-pressure-controlling device for a hydraulic motor coupled to a large inertial load comprising:

a valve body including first and second independent bores formed therein,

a first pair of inlet and outlet ports hydraulically coupled to said first bore and hydraulically connected respectively to a source of pressurized oil and a tank through a directional control valve,

a pair of annular chambers hydraulically coupled to said second bore and connected to intake and exhaust passages to said hydraulic motor,

a slidable valve seat cylinder carried by said second bore between said pair of annular chambers and axially slidable between limits and defining a common bypass passage between said intake and exhaust passages of said hydraulic motor,

poppet valves operatively associated with the slidable valve spool and said intake and exhaust passages to said hydraulic motor to insure that regardless of the position of the directional control valve, the exhaust oil passage is automatically opened or closed, depending upon the pressure of the oil in the hydraulic motor exhaust passage.

2. The oil-pressure-controlling device as claimed in claim I, further comprising: slidable spring seats carried by said second bore at the end of each spring opposite that of said plunger, oil pressure passage means extending between said plunger and said slidable spring seat, whereby upon an increase in oil pressure, the spring seat is moved to further com re ss the spring and to thereby effect sprrng pressure biasing 0 said plunger in two steps to prevent abrupt pressure increase due to the presence of said large inertial load.

3. The oil-pressure-controlling device as claimed in claim 1, further comprising a nozzle centrally disposed within each of said annular chambers and operatively coupled to the common bypass passage for inducting pressurized oil from said oil supply passage by discharge of the bypass oil through said nozzle from said bypass passage.

4. The oil-pressure-controlling device as claimed in claim 2, further including an annular chamber positioned in the oil supply passage and a nozzle centrally disposed within said annular chamber and operatively coupled to said common bypass passage for inducting pressurized oil from said oil supply passage by nozzle discharge of bypass oil.

5. The oil-pressure-controlling device as claimed in claim 1, wherein said relief valve comprises a valve seat, a poppet valve disposed against the open end of a small shaft hole within said valve seat, said poppet valve having a sharply pointed head portion formed at an obtuse angle at one end thereof and abutting said valve seat on one end thereof and having a plurality of passages extending axially on the outer surface thereof with said plungers disposed at opposite ends of the bypass passage. 

1. An oil-pressure-controlling device for a hydraulic motor coupled to a large inertial load comprising: a valve body including first and second independent bores formed therein, a first pair of inlet and outlet ports hydraulically coupled to said first bore and hydraulically connected respectively to a source of pressurized oil and a tank through a directional control valve, a pair of annular chambers hydraulically coupled to said second bore and connected to intake and exhaust passages to said hydraulic motor, a slidable valve seat cylinder carried by said second bore between said pair of annular chambers and axially slidable between limits and defining a common bypass passage between said intake and exhaust passages of said hydraulic motor, plungers carried by said second bore on opposite sides of said valve seat cylinder, springs biasing each plunger in pressure contact with the respective ends of said slidable valve seat cylinder, the oil pressure of either said intake or exhaust passage of said hydraulic motor upon reaching a predetermined value causes the valve seat cylinder to slide to a predetermined limit position to open the bypass passage between the exhaust and intake passages of said hydraulic motor, a high-pressure crossover relief valve means for each plunger, a slidable valve spool carried by said first bore, poppet valves operatively associated with the slidable valve spool and said intake and exhaust passages to said hydraulic motor to insure that regardless of the position of the directional control valve, the exhaust oil passage is automatically opened or closed, depending upon the pressure of the oil in the hydraulic motor exhaust passage.
 2. The oil-pressure-controlling device as claimed in claim 1, further comprising: slidable spring seats carried by said second bore at the end of each spring opposite that of said plunger, oil pressure passage means extending between said plunger and said slidable spring seat, whereby: upon an increase in oil pressure, the spring seat is moved to further compress the spring and to thereby effect spring pressure biasing of said plunger in two steps to prevent abrupt pressure increase due to the presence of said large inertial load.
 3. The oil-pressure-controlling device as claimed in claim 1, further comprising a nozzle centrally disposed within each of said annular chambers and operatively coupled to the common bypass passage for inducting pressurized oil from said oil supply passage by discharge of the bypass oil through said nozzle from said bypass passage.
 4. The oil-pressure-controlling device as claimed in claim 2, further including an annular chamber positioned in the oil supply passage and a nozzle centrally disposed within said annular chamber and operatively coupled to said common bypass passage for inducting pressurized oil from said oil supply passage by nozzle discharge of bypass oil.
 5. The oil-pressure-controlling device as claimed in claim 1, wherein said relief valve comprises a valve seat, a poppet valve disposed against the open end of a small shaft hole within said valve seat, said poppet valve having a sharply pointed head portion formed at an obtuse angle at one end thereof and abutting said valve seat on one end thereof and having a plurality of passages extending axially on the outer surface thereof with said plungers disposed at opposite ends of the bypass passage. 